1. Field of the Invention
The invention discloses the synthesis of a bifunctional perovskite compound, particularly to the synthesis of a bifunctional perovskite compound used as the cathode of fuel cell.
2. Description of the Prior Art
The fuel cell has been recognized as green environmental energy with excellent development potential in the 21st century. As for the research of fuel cell at present, the main research direction is the Proton Exchange Membrane Fuel Cell (PEMFC) and the Direct Methanol Fuel Cell (DMFC). In the PEMFC system, the anode uses hydrogen as the reactant. The source of hydrogen is mainly from the natural gas. Even though the conversion rate is high, there are still storage problems. In the DMFC system, the serious diffusion of methanol will shorten the life of cell. The conversion rate is low and the anodic platinum catalyst is easy to be poisoned by the carbon monoxide. These problems should be solved urgently. As for the comparison, the alkaline fuel cell has been successfully used in the electronic produce with low power consumption, due to the advantages, such as simple structure, high energy density, stable performance, high electricity generation efficiency and low environmental impact etc.
In the alkaline fuel cell system, the cathode is oxygen diffusion electrode, and the electrolyte is the alkaline solution, such as potassium hydroxide etc. Compared to the acid electrolytic solution system, the reduction rate of oxygen is faster in the alkaline electrolytic environment. In addition, the corrosion rate of metal is much lower under the alkaline solution compared to the acid solution as well. Thus, non-platinum system can be used as the catalyst to reduce the cost, which is the greatest advantage for the alkaline fuel cell. Compared to the anode, the cathode has larger electric current and potential when the electrochemical reaction takes place. Thus, the quality of cathodic air electrode plays a very important role.
In many previous literatures, it is known that many kinds of catalyst can be used for accelerating the oxygen reduction, wherein the platinum or platinum alloy has the highest reduction efficiency. However, due to the price of platinum is too expensive and the selectivity of platinum is too low, so that the research trend is towards to look for the catalyst which can substitute the platinum and can own high catalysis activity, such as the perovskites, spinels, pyrochlores, metal chelating compound, metal or metal and metal oxide mixture.
In various catalysts, the research of perovskites is paid much more attention. It has been understood that the perovskites own good catalysis property in the oxygen reduction condition. On the other side, in 2005, S. Trasatti et al. discovered that the ruthenium tin oxide alloy had there is remarkable oxygen generation ability in the electrochemical reaction. One of the improvement trends is to develop a catalyst with good electrochemical effect for the oxidization and reduction of oxygen at the same time, and can be applied to the recharable alkaline fuel cell and various metal air cells.